Quick answer: Unreal MassAgent ORCA avoidance producing spiral patterns in dense crowds? ORCA's pair-wise resolution causes oscillation - raise iteration count or use blended ORCA-RVO.
200 NPCs in a market scene. Instead of moving naturally, they form rotating spirals.
Raise ORCA iterations
mass.Avoidance.ORCAIterations 8More iterations = better convergence in dense scenes. Default 3 is fine for sparse; not crowds.
Or use a different avoidance
RVO (reciprocal velocity obstacles) handles crowds better than ORCA in some configurations. Test both.
Reduce neighbor sample
Each agent considers N neighbors. For crowds, N=8 is enough; more causes the oscillation.
“Crowd avoidance is a tuning problem with no universal answer.”
If your game has crowd scenes, dedicate a sprint to crowd tuning. The bug class is endless without focused tuning time.